21451323556 has 24 divisors (see below), whose sum is σ = 40675531904. Its totient is φ = 9839867040.

The previous prime is 21451323547. The next prime is 21451323557. The reversal of 21451323556 is 65532315412.

It is not an unprimeable number, because it can be changed into a prime (21451323557) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1256940 + ... + 1273891.

Almost surely, 2^21451323556 is an apocalyptic number.

21451323556 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21451323556 is a deficient number, since it is larger than the sum of its proper divisors (19224208348).

21451323556 is a wasteful number, since it uses less digits than its factorization.

21451323556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2531011 (or 2531009 counting only the distinct ones).

The product of its digits is 108000, while the sum is 37.

Adding to 21451323556 its reverse (65532315412), we get a palindrome (86983638968).

The spelling of 21451323556 in words is "twenty-one billion, four hundred fifty-one million, three hundred twenty-three thousand, five hundred fifty-six".